<snip>
I thought of that, and CF supports LDAP natively, but I don't think you can
access NT domain authentication over LDAP. It would be a great solution if
we were creating a new authentication database, but we need to leverage the
existing NT usernames/passwords.
</snip>
Looks like you can use LDAP if you implement a 2000 server on the network...
here's part of a thread discussing this
http://www.openldap.org/lists/openldap-general/200010/msg00047.html